1. Field of the Invention
The present invention relates to thin-film magnetic heads, and more particularly, relates to a thin-film magnetic head having improved abrasion-resistance in a face opposing a recording medium.
2. Description of the Related Art
Since thin-film magnetic heads having magnetoresistive devices can better meet the need for the further narrowing of tracks compared with conventional bulk-type magnetic heads, thin-film magnetic heads in various forms have been applied to sliding-type magnetic heads which slide relative to a tape medium having high writing density and to floating-type magnetic heads which move relative to a magnetic disk without contacting therewith.
A sliding-type magnetic head having a conventional thin-film magnetic head will be described with reference to the figures.
FIG. 15 is a perspective view of a conventional sliding-type magnetic head, FIG. 16 is a plan view of a major portion of the sliding-type magnetic head observed from an opposing face opposing a recording medium side, and FIG. 17 is a cross-sectional view taken along the line XVIIxe2x80x94XVII in FIG. 16.
A sliding-type magnetic head B shown in FIG. 15 is formed in an overall block shape, in which half-cores (substrates) 202 and 203 in the form of blocks are adhered to each other at side edge surfaces thereof with an in-core layer 5 therebetween. One side surface of a block formed of the half-cores 202 and 203 is fixed on a mounting plate 201 by adhesive so that a small portion of the block formed of the half-cores 202 and 203 protrudes out from the edge of the mounting plate 201.
One surface of the sliding-type magnetic head B protruding out from the mounting plate 201 is processed so as to have a curved convex shape, and the surface having the curved convex shape is used as a sliding face 206 sliding on a magnetic recording medium such as a magnetic tape.
As shown in FIGS. 16 and 17, a writing head (hereinafter referred as to an inductive head) 210 for writing and a thin-film magnetic head 211 for reading, provided with a magnetoresistive device, are embedded in the in-core layer 205.
The thin-film magnetic head 211 is composed of a lower shield layer 101, a lower insulating layer 104, a magnetoresistive device (hereinafter referred to as an MR device) 105, an upper insulating layer 106, and an upper shield layer 107, which are sequentially formed on the half-core 202.
As shown in FIG. 16, the edge faces of the lower shield layer 101, the lower insulating layer 104, the MR device 105, the upper insulating layer 106, and the upper shield layer 107 are exposed at the sliding face 206 sliding on a magnetic recording medium.
A reading magnetic gap G is formed by the lower insulating layer 104 and the upper insulating layer 106.
The upper shield layer 107 and the lower shield layer 101 are composed of, for example, a nickel-iron (NiFe) alloy; the upper shield layer 107 is formed by plating, and the lower shield layer 101 is formed by sputtering.
In addition, the upper insulating layer 106 and the lower insulating layer 104 are composed of, for example, Al2O3, and are formed by sputtering.
In the structure shown in FIGS. 16 and 17, the upper shield layer 107 is also used as a lower core layer for the inductive head 210 formed on the upper shield layer 107, a writing gap layer 110 is formed on the lower core layer (the upper shield layer) 107, a coil layer 111 patterned so as to be planar and spiral is formed on the writing gap layer 110, the coil layer 111 is surrounded with a coil insulating layer 112, and a front portion 113a of an upper core layer 113 formed on the coil insulating layer 112 opposes the lower core layer 107 at a minute distance therefrom with the writing gap layer 110 therebetween at the sliding face 206. A base portion side 113b of the upper core layer 113 is magnetically coupled with the lower core layer 107. In addition, a protective layer 116 is formed over the upper core layer 113. Numeral reference 108 in FIG. 17 indicates electrodes for detection connected to the MR device 105, and the electrodes 108 are connected to both sides of the MR device 105.
The sliding-type magnetic head B is produced by, for example, the steps as described below. The in-core layer 205 is first formed by sequentially forming the thin-film magnetic head 211 and the inductive head 210 by a thin-film formation technique on the half-core 202, and the other half-core 203 is then adhered to the in-core layer 205 so as to form the core block. Subsequently, one surface of the core block is polished by a polishing tape having a polishing powder composed of diamond or the like dispersed thereon so as to form the sliding face 206 having a curved convex shape, whereby the sliding-type magnetic head B is obtained.
However, in the sliding-type magnetic head B, since the upper and the lower shield layers 107 and 101, which sandwich the upper and lower insulating layers 106 and 104, are formed of a NiFe alloy having relatively low hardness, when the core block is polished by the polishing tape, the surfaces of the upper and the lower shield layers 107 and 101, which are polished, may be stretched, and as a result, sags D in the form of a tongue may be formed as shown in FIG. 16. In some cases, the sags D in the form of a tongue may extend from, for example, the upper shield layer 107 to the MR device 105 or the lower shield layer 101, and hence, there is a problems in that short-circuiting between the upper and the lower shield layers 107 and 101 and the MR device 105 may occur.
In addition, when the sliding-type magnetic head B slides relative to a magnetic tape or the like in order to read the magnetic writing information, the sliding face 206 of the head is actually polished by the magnetic tape, and in a manner similar to that described above, the shield layers 107 and 101 may be stretched so as to form the sags D.
Furthermore, recently, in order to respond to the need for higher magnetic writing density, the distance between the upper and the lower shield layers 107 and 101, i.e., the magnetic gap G, must be reduced. Accordingly, the upper and the lower insulating layers 106 and 104 tend to be thinner, and in this case, even when smaller sags are formed, the shield layers 107 and 101 are readily brought into contact with each other, whereby there is a problem in that short-circuiting is more likely to occur.
Taking the problems described above into consideration, an object of the present invention is to provide a thin-film magnetic head having a structure which prevents short-circuiting, in which, even if sags in a shield layer are formed when a sliding face sliding relative to a recording medium is polished, the sags do not reach an MR device or another shield layer.
To these ends, the present invention employs the following structure.
A thin-film magnetic head according to the present invention comprises a laminate comprising a magnetoresistive device for reading information by moving relative to a magnetic recording medium, insulating layers provided on both sides of the magnetoresistive device in the thickness direction thereof, and shield layers provided on each insulating layer, and a substrate on which the laminate is provided, in which the magnetoresistive device, the insulating layers, and the shield layers are exposed at an opposing face opposing a recording medium, wherein at least one of the shield layers in contact with the insulating layers comprises a magnetic layer and a rigid layer which is harder than the magnetic layer and is in contact with the insulating layer.
In the thin-film magnetic head described above, since at least one of the two shield layers with the magnetoresistive device provided therebetween is composed of a magnetic layer and a rigid layer, and since it is exposed at the opposing face opposing a recording medium, the rigid layer is not stretched in the form of a tongue due to relatively high hardness thereof even when the opposing face opposing a recording medium is polished, whereby the short-circuiting between the rigid layers or between the magnetoresistive device and the rigid layer will not occur.
In addition, even if the magnetic layer having relatively low hardness is stretched so as to form a sag in the form of a tongue when the opposing face opposing a recording medium is polished, since the rigid layer is disposed between the magnetic layer and the insulating layer, the sag is unlikely to reach the magnetoresistive device, and as a result, the probability of short-circuiting between the magnetoresistive device and the shield layer can be reduced.
In the thin-film magnetic head according to the present invention, at least one of the rigid layers may comprise a soft magnetic CoZrNb-based material.
According to the thin-film magnetic head mentioned above, since the rigid layer is composed of a soft magnetic CoZrNb-based material, and the rigid layer has both high hardness and soft magnetic properties, a shield layer which is able to prevent short-circuiting caused by sags, in addition to having superior shielding properties, can be formed.
In the thin-film magnetic head according to the present invention, at least one of the rigid layers may be a soft magnetic layer formed by sputtering.
In particular, the rigid layer is preferably composed of the same material as that of the magnetic layer.
In general, a layer formed by sputtering is a very dense layer and has high hardness.
Accordingly, since a soft magnetic layer formed by sputtering is used as a rigid layer, the rigid layer can provide high hardness, so that a shield layer having the ability to prevent short-circuiting caused by sags, in addition to having superior shielding properties, can be formed.
In the thin-film magnetic head according to the present invention, the rigid layer disposed further from the substrate than the magnetoresistive device may comprise a rigid base layer composed of a soft magnetic CoZrNb-based material in contact with the insulating layer and a rigid adhesive layer composed of the same material as that for the magnetic layer in contact therewith, and the rigid adhesive layer may be formed by sputtering.
According to the thin-film magnetic head mentioned above, since the rigid base layer is formed on the insulating layer, and since the rigid adhesive layer composed of the same material as that for the magnetic layer is formed between the rigid base layer and the magnetic layer by sputtering, separation between the rigid base layer and the magnetic layer can be prevented by the rigid adhesive layer.
That is, the rigid layer is formed by sputtering in order to increase hardness, and alternatively, the magnetic layer may be formed by plating in some cases.
In the case mentioned above, it is difficult for the rigid base layer and the magnetic layer to adhere to each other due to the difference in the film forming method, in addition to the difference in the material therebetween, and as a result, separation may occur in some cases.
Accordingly, when the rigid adhesive layer composed of the same material as that for the magnetic layer is formed between the rigid base layer and the magnetic layer by sputtering, the separation between the rigid base layer and the magnetic layer can be prevented since the rigid adhesive layer has superior adhesion to both rigid base layer and magnetic layer.
In the thin-film magnetic head of the present invention, the thickness of the rigid layer may be greater than the distance between the shield layers.
According to the thin-film magnetic head mentioned above, since the thickness of the rigid layer is set to be greater than the distance between the shield layers, and hence, the thickness of the rigid layer is greater than the magnetic gap length of the thin-film magnetic head, the distance between the magnetoresistive device and the individual magnetic layers can be sufficiently great, whereby the probability of short-circuiting between the shield layer and the magnetoresistive device can be significantly decreased even when sags in the magnetic layer occur.
In the thin-film magnetic head of the present invention, the CoZrNb-based material may be represented by the formula CoxZr Nbz, in which the x, y, and z, representing the composition ratios on an atomic percent basis, are 78%xe2x89xa6xxe2x89xa692%, y=a(100-x)%, and z=(100-x-y)%, and xe2x80x9caxe2x80x9d is 0.1xe2x89xa6axe2x89xa60.5.
According to the thin-film magnetic head described above, since the rigid layer is composed of the CoZrNb-based material having the composition described above, and the material having this composition has high hardness in addition to superior magnetic characteristics, a shield layer which can prevent short-circuiting caused by sags, in addition to having superior shielding properties, can be formed.
In the thin-film magnetic head of the present invention, the CoZrNb-based material may be represented by the formula CoxZryNbzTv, in which the T is at least one element selected from the group consisting of gold (Au), palladium (Pd), chromium (Cr), rhodium (Rh), and ruthenium (Ru), the x, y, z, and v, representing the composition ratios on an atomic percent basis, are 78%xe2x89xa6xxe2x89xa692%, y=a(100-x)%, 0%xe2x89xa6vxe2x89xa64%, and z=(100-x-y-v)%, and xe2x80x9caxe2x80x9d is 0.1xe2x89xa6axe2x89xa60.5.
According to the thin-film magnetic head described above, since the CoZrNbT-based material containing an element T in the CoZrNb-based material is used, and the CoZrNbT-based material has superior corrosion resistance in addition to high hardness, a shield layer can be formed, which has superior shielding properties, ability to prevent short-circuiting caused by sags, and superior corrosion resistance.
In addition, instead of the CoZrNb-based material, a CoTaZr-based material represented by the formula CoaTabZrc may be used, in which the a, b, and c, representing the composition ratios on an atomic percent basis, are 85%xe2x89xa6axe2x89xa695%, 2%xe2x89xa6bxe2x89xa615%, and 2xe2x89xa6cxe2x89xa610%.
In addition, instead of the CoZrNb-based material, a CoTaHf-based material represented by the formula CosTatHfu may be used, in which the s, t, and u, representing the composition ratios on an atomic percent basis, are 85%xe2x89xa6axe2x89xa695%, 2%xe2x89xa6txe2x89xa615%, and 2xe2x89xa6uxe2x89xa610%.